Unrefined hydrocarbons such as crude oil, resids and bottom streams often contain finely divided solid matter, which often must be removed prior to further use or processing. These solids can include solids of a soil-like nature, finely divided silicas, clays, silt and coke, and metal oxide and sulfide corrosion solids. These solids may also include traces of metal particles such as lead, nickel, chromium and the like, and salts thereof.
For instance, fluid catalytic cracker (FCC) units use a fluidized bed of zeolite type aluminosilicate clay particles to crack heavy petroleum fractions into lighter fractions at elevated temperatures. The catalyst is eventually deactivated by poisoning or coking. These spent fines must be removed from the FCC on a continual basis so that slurry containing fresh catalyst can be added.
Some of this slurry oil containing the spent fines is then typically settled in tankage, though hydrocyclones are sometimes used to accelerate the separation process. Both native and synthetic components of the slurry oil have a dispersant effect which retards the settling of the fines.
The present inventor has discovered that a combination of certain chemical agents, when added to the slurry oil, have an anti-dispersant or coagulant effect which accerlates the settling process. This produces a cleaner decant oil (typically <0.05 wt % ash) in a shorter period of time, and can then be sold as carbon black feedstock or residual fuel oil.